The present invention relates to new alkoxylated aminopolyethers, a process for their preparation and coal/water slurries containing them.
Slurries of finely ground mineral coal in water are known, for example, from U.S. Pat. No. 4,358,293, U.S. Pat. No. 4,302,212, Japanese Patent Application No. 58-125,787 and Japanese Patent Application No. 57-145,190. On the one hand, they can be transported inexpensively through pipelines, and on the other hand they can be burned directly in existing combustion plants. Coupling of transportation with subsequent combustion is particularly advantageous. The coal/water slurries can also be prepared immediately before combustion and then burned. Problem-free handling from the safety point of view is an advantage here.
In the preparation of coal/water slurries, it is found that, without the addition of auxiliaries, the viscosity of the slurries increases over-proportionally as the solids content increases and the slurry solidifies when it is still far below a coal concentration which allows use of the slurries as fuel.
Various measures can be taken to improve the flow properties of coal/water slurries. According to U.S. Pat. No. 3,762,897 and U.S. Pat. No. 4,282,006, a particular distribution of the particle sizes of the coal employed leads to an improvement in the flow properties, while according to U.S. Pat. No. 4,282,006, anionic surface-active compounds are additionally used. The use of anionic or cationic surfactants, high molecular weight substances and polyelectrolytes in the preparation of aqueous coal slurries is furthermore known (see U.S. Pat. No. 4,104,035, U.S. Pat. No. 4,304,572, U.S. Pat. No. 3,524,682, EP-OS (European Published Specification) No. 41,337, JP-OS (Japanese Published Specification) No. 56-067,396 and JP-OS (Japanese Published Specification) No. 56-088,495). Non-ionic alkylene oxide copolymers ethoxylated with at least 100 ethylene oxide units are described as surface-active substances for coal/water slurries in U.S. Pat. No. 4,358,293, alkylphenols, propylene glycol or alkylenediamines being used as starter molecules. JP-OS (Japanese Published Specification) No. 58-125,787 describes branched, non-ionic and nitrogen-containing alkylenepolyethers, and U.S. Pat. No. 4,302,212 and JP-OS (Japanese Published Specification) No. 57-145,190 describe polyalkylene oxides built up from starter molecules containing hydroxyl groups.
However, the known surface-active substances are not satisfactory for commercial use, since the aqueous coal slurries thus prepared have such high viscosities, especially at higher solids contents, such that they are difficult to handle in industry as mixtures with good flow properties.